A continuously variable transmission (CVT) can change steplessly through an infinite number of transmission torque ratios between and inclusive of a calibrated maximum and a minimum transmission torque ratio. A typical CVT includes a variator assembly having two pulleys, i.e., a drive pulley and a driven pulley. A belt or other drive mechanism is disposed between sheaves of both of the pulleys. Other CVT designs may use conical rollers in lieu of a belt. Frictional engagement of the belt with the sheaves transfers torque from the drive pulley to the driven pulley, with the drive pulley being connected to an input member of the CVT and the driven pulley being connected to an output member.
The transmission torque ratio of a CVT is the ratio of an amount of torque carried by the driven pulley to an amount of torque carried by the drive pulley. The transmission torque ratio may be varied by moving the sheaves of a designated one of the pulleys closer together, while at the same time moving the sheaves of the other pulley farther apart. Movement in this manner causes the belt to ride higher or lower on the respective pulleys. As the vehicle accelerates, the spacing of the sheaves may be varied. Proper diagnostics of a variator assembly in a CVT may help to ensure optimal ongoing performance of the CVT.